I had this problem in earlier versions (maybe 12.04, not sure), but it was corrected. Recently the bug returned for me.
Ubuntu: 14.04-64 LTS version fresh install. Computer: Dell Inspiron Notebook Processor: Intel® Core™ i7-3632QM CPU @ 2.20GHz × 8 Graphics: Intel® Ivybridge Mobile Driver: X.Org X server - AMD/ATI display driver wrapper xserver-xorg-video-ati opensource Memory: 8GiB
I had this problem in earlier versions (maybe 12.04, not sure), but it was corrected. Recently the bug returned for me.
Ubuntu: 14.04-64 LTS version fresh install. xorg-video- ati opensource
Computer: Dell Inspiron Notebook
Processor: Intel® Core™ i7-3632QM CPU @ 2.20GHz × 8
Graphics: Intel® Ivybridge Mobile
Driver: X.Org X server - AMD/ATI display driver wrapper xserver-
Memory: 8GiB